Positron Emission Tomography (PET) has become an important tool in the fight against cancer. PET is now being used in diverse studies ranging from basic research in animal models of cancer in the mouse, through to diagnosis and staging of cancer patients in the clinic. It is clear that PET technology is playing a prominent and an increasingly visible role in modem cancer research and clinical diagnosis. However, there is an urgent need for improvement in PET instrumentation in order to exploit full potential of this promising technique. In order to address the limitations in the existing detector technology used in PET systems, particularly the photomultiplier tubes used for optical readout of scintillators, we propose to investigate a novel, solid state position sensitive optical detector technology. This new optical detector technology can be used to build high resolution PET modules, which can be utilized in PET systems suitable for clinical whole body imaging as well as dedicated, high resolution systems for breast and small animal imaging. The proposed Phase I project will aim to demonstrate the feasibility of this concept.